Variation between individual cows in in situ rumen degradation characteristics of maize and grass silages

Abstract

Different numbers of animals have been used in different studies to cover the variation between individual animals in in situ rumen degradation characteristics of maize and grass silages. The objective of this study was to determine whether three cows are sufficient or not to cover the variation between individual cows in in situ rumen degradation characteristics of dry matter (DM), organic matter (OM), crude protein (CP), starch and neutral detergent fibre (NDF) for maize and grass silages. Fifteen maize and 15 grass silage samples, with a broad range in chemical composition, were selected. The maize and grass silage samples were incubated in the rumen for 2, 4, 8, 16, 32, 72 and 336 h, using the nylon bag technique. Three cows were used for nylon bag incubation of maize silages and three other cows for grass silages. The variation between individual cows was found significant (P <0.05) for degradation rate (kd) of DM, OM and CP, and the effective rumen degradation (ED) of DM and CP of maize silages whereas non-significant (P > 0.05) differences were found for all other parameters of DM, OM, CP, starch and NDF. The variation between individual cows was found non-significant (P > 0.05) for rumen undegradable fraction (U), potentially rumen degradable fraction (D), kd and ED of DM, OM, CP and NDF of grass silages. The results of this study indicate that the use of three cows for nylon bag incubations of grass silages is sufficient whereas the use of three cows for nylon bag incubations of maize silages is not sufficient to cover variation between the individual cows.